The presently disclosed subject matter relates to a blood measuring apparatus which performs a blood measurement by employing the electric resistance method.
JP-A-59-184841 discloses a configuration where, in order to correctly measure blood cells by employing the electric resistance method, a blood sample is caused to flow through the center of an aperture (sensing hole) by using a sheath flow on the upstream side of the aperture, thereby obtaining clean blood cell pulses. Also in such a configuration where a sheath flow is used upstream of an aperture, however, recirculation of blood cells occurs downstream of the aperture, and there arises a problem in that a measurement error is caused.
On the other hand, JP-A-2001-264233 and JP-T-2003-501621 disclose apparatuses having a configuration where, in the downstream side of an aperture, large blood cells which impede measurement of platelets are blocked from recirculating to the aperture, by using a back sheath or a sweep sheath. In measurement by such an apparatus, blood cells which have passed through the aperture do not recirculated to the sensing region in the aperture, and therefore a measurement error can be prevented from occurring.
In the configuration of a back sheath or a sweep sheath, however, blood cells are recovered before the jet flow defuses. Therefore, a mechanism for this purpose must be attached to the vicinity of the aperture, and hence the configuration is complicated. In the configuration, moreover, a sheath liquid is flown through a recovery pipe. Consequently, the flow is weak in the vicinity of the aperture, and therefore it is difficult to remove floating blood cells, bubbles adhering to, for example, a partition wall in which the aperture is formed.
To comply with the above, the applicant has proposed in JP-A-2012-127680 a blood measuring apparatus in which a swirling flow is generated by sucking a diluting solution on the downstream side of an aperture to block blood cells from recirculating to a sensing region, whereby measurement is prevented from being erroneously performed.
The blood measuring apparatus provided by the applicant achieves the very excellent effects as described above. The presently disclosed subject matter has been conducted in order to provide a further improved blood measuring apparatus.